The document FR 2 691 520 describes a sealed and thermally insulating tank having, in succession, through the thickness, from the inside toward the outside of the tank, a primary sealing membrane in contact with the fluid contained in the tank, a primary thermal insulating barrier, a secondary sealing membrane, a secondary thermal insulating barrier, and a support structure consisting of metal plates forming the hull or the double hull of a merchant ship such as a gas carrier. The corner areas of the tank are made from a pre-assembled corner structure of dihedral form, shown in FIG. 3 of document FR 2 691 520.
A pre-assembled corner structure comprises two beveled insulating plates joined by means of a corner joint and forming the secondary insulating barrier, a flexible membrane resting against the insulating plates of the secondary insulating barrier and forming the secondary sealing barrier, and two other beveled insulating plates, joined by means of a corner joint and forming the primary insulating barrier. This corner structure is advantageous in that it enables the corner structures to be pre-assembled in the workshop. However, these corner structures are heavy and bulky, making them difficult to transport and handle. The manufacture of these structures is also relatively complicated.